Conventional electrical systems within residential and commercial buildings have a plurality of interconnecting electrical conduits joined to each other and to junction boxes with adapters. Although a number of metallic junction boxes exist on the market, the preferred approach is to use polyvinyl chloride (PVC) electrical conduit and junction boxes which are less costly and easier to install.
One type of junction box in use includes a plurality of open ports into which electrical conduit must be placed to seal the box. The open ports which are not in use must be independently sealed when not in use to prevent concrete and other material from entering the junction box. This has proven disadvantageous, since sealing open ports requires separate components, additional time and additional expense. There also exists the risk that some of the open ports which require sealing will be missed during installation, exposing electrical wiring to contamination. This is a particular problem where the space surrounding the junction box is filled with concrete.
Another conventional junction box includes a number of knockout regions which may be opened to allow for access into the box. This junction box requires separate adapters which must be fitted into the knockout region in order to connect the electrical conduit to the box and results in additional assembly time and expense.
Examples of the above junction boxes and other related boxes can be found in U.S. Pat. Nos. 3,139,480, 4,845,312, 4,896,784 and 5,051,541.
There are a number of different adapters in use to couple electrical conduit, and in particular flexible corrugated electrical non-metallic tubing (ENT), to a conventional junction box. An example of such an adapter can be found in U.S. Pat. No. 4,836,580 where there is provided a conduit connector for joining corrugated conduit to a junction box. While the connector disclosed provides an improvement over the prior art, it requires a very complex mold and must be screwed onto the sidewall of a junction box which itself must be adaptive to the connector. In the context of modern residential and commercial developments where thousands of junction boxes may be required, each on average requiring four connectors, using the conduit connector in '580 presents a labor intensive exercise. Another example of a connector for flexible electrical conduit can be found in U.S. Pat. No. 4,880,387, for which the same problems arise.
In Canadian Patent Application No. 2,085,394 there is provided an improved junction box having knockouts located within tubular projections. When a knockout is removed, a locking ring is formed within the respective tubular projection capable of receiving and retaining flexible corrugated ENT. Although the junction box in '394 provides an improvement over the prior junction boxes, there continues to exist a need in the art for a junction box which is capable of retaining flexible corrugated ENT to the box even under large forces. In particular, many jurisdictions require that junction boxes conform to strict building standards which often require that a junction box meet or exceed pull tests of 150 lbs or more.
Another problem presented by existing junction boxes is the difficulty which arises in feeding electrical wiring between two junction boxes joined by electrical conduit. Conventional designs provide for the electrical conduit to be coupled to a junction box at a tubular extension with an adapter which orients the conduit orthogonally with an outer wall of the box. In such an arrangement it is difficult for an installer to feed wiring between two boxes and the wiring is regularly bent out of shape.
Accordingly, it is an object of the invention to provide an improved junction box which fulfills the above needs. It is a further object of the invention to provide a junction box lid which reinforces the ability of a junction box to retain flexible corrugated tubing.